Google Earth and Geoscience EducationPeter Selkin, University of Washington, Tacoma
Introduction: What is Google Earth
Google Earth is a virtual globe browser, arguably the most popular of those available for free on the Internet (NASA's World Wind and ESRI's upcoming ArcGIS Explorer are competitors). Virtual globes allow users to interactively display and investigate geographic data (primarily satellite and aerial images and terrain models, but also 2- and 3-D vector data such as earthquake locations, water bodies, and buildings). One of the most useful aspects of Google Earth from a geoscience education point of view is the availability of a variety of geoscience-related datasets for free on the web.
Google Earth allows users to perform some basic measurements (latitude and longitude, elevation, and size), which has led some users to consider it a variety of GIS software. Geoscience professors should be careful when making this comparison. Alan Glennon, a graduate student in geography at UCSB, wrote two essays on the pros and cons of so-called "naive" GIS (mainly focusing on applications such as Google Earth). The essays (and the comments on them by other geographers) are a good starting point if you are trying to decide whether to use a virtual globe such as Google Earth or a full-featured GIS such as ArcGIS or GRASS in the classroom. (also see Glenn Richard's Google Earth or GIS? section from the SERC Teaching with Google Earth website.
Keeping up with Google Earth: Resources
- Nature and Slate articles about Google Earth.
- Google Earth Community Forums and FAQ
- Frank Taylor's Google Earth Blog
- Stefan Geens' Ogle Earth blog
- Tutorials by podcast from KoKae Screencasts
- News about Google Earth and the official Google Blog.
- An explanation of the origin of Google Earth by one of its original programmers.
How to Obtain a Copy
The Google Earth browser is a separate application from your web browser. As of July 16, 2006, the current stable version (v.3) runs on both Windows 2000/XP and Mac OSX (10.3.9 and higher). A beta version (v.4) runs on Windows, Mac OSX, and Linux platforms. The Google Earth browser can be downloaded from http://earth.google.com/.
Several upgrades to the Google Earth software are available. This discussion covers the standard version (available for free for personal or educational use). I do not have experience with the "plus" ($20) or "pro" ($200+) upgrades.
Using Google Earth
Getting Around in Google Earth: Common FunctionsNavigation in Google Earth will be fairly intuitive for students who have grown up in an age of clicking and dragging, mouse wheels, and video games. Those who are not familiar with the interface may wish to take a look at one of the guides in the text box below. These guides describe the basics of browsing in Google Earth better than I can. Nonetheles, I will summarize some of the basics here.
Google Earth allows the user to view true-color images draped over topography for most of the globe, at varying resolutions mainly depending on the browser's "eye altitude" (height above ground). The user can navigate (pan) either by clicking and dragging part of the field of view with the mouse, by using the arrow keys, or by using a set of navigation arrows displayed in the main Google Earth viewer window. The window's viewpoint can be rotated relative to the virtual globe using a sliding or rotating control on the viewer window. The viewpoint can zoom into the globe using a slider control, the mouse wheel (PC) or control-clicking and dragging (Mac). The viewpoint can also "tilt" from a vertical position to a nearly horizontal poisition (again using a slider control).
Google Earth's main attraction, however, has been its ability to display vector datasets (placemarks - points, lines, and polygonal areas), raster images (overlays), and 3D virtual models on top of the virtual globe. Although some placemarks and overlays are supplied with Google Earth or are directly accessible through Google Earth in the "Google Earth Community", the majority must be downloaded from the Web. Placemarks and overlays are discussed in more detail later.
3D models of buildings in some cities are provided with Google Earth (the "Buildings" layer), but to get the most use out of 3D models, you will have to download the SketchUp plugin. This will allow you to build and use 3D objects in Google Earth. Although 3D models are fun to play with, they are less broadly useful than other types of placemarks, so I won't go into them in detail. One clever use of 3D models in an educational context, however - an exercise on visualizing wind farms - is from Noel Jenkins' Juicy Geography site.
You and your students will probably find it useful to be able to measure features in Google Earth. Here are a few hints on how to make a couple of different measurements:
- Position: The latitude and longitude of the mouse pointer are shown in the status bar near the bottom of the screen. An option in the Preferences dialog box allows you to change whether position is displayed in degrees-minutes-seconds format or decimal degrees.
- Elevation: The elevation of the mouse pointer is also listed at the bottom of the screen. The "eye alt" value is the elevation of your viewpoint. An option in the Preferences dialog box allows you to change whether elevation is displayed in feet or meters.
- Distances: Google Earth allows you to measure the great circle distance from one point to another or along a path (through several points), Distances are measured as the crow flies, without taking topography into account (as far as I can tell). In Google Earth 3, the measurement tool is found under the "Tools" menu. In Google Earth 4, the measurement icon appears as a ruler at the top of the window.
- Vertical exaggeration can also be changed in the Preferences dialog box.
One final note about Google Earth navigation: The top panel on the left side of the Google Earth window ("Search") allows the user to search for a location. In my experience, the search function is not perfect: a search for Augustine Volcano, for example, returns no results, and a search for "Mount Rainier" after a search for "Tacoma, WA" returns local businesses with the word "Rainier" in their names. Latitude and longitude can be used instead of a place name for less ambiguous searching.
Guides to Google Earth Navigation
- Basics of Google Earth from Frank Taylor's Google Earth Blog.
- Google's tour of Google Earth.
- The Visual Guides at Juicy Geography - includes printable guides that can be used as mousepads.
- A set of guides from GE Lessons (some are QuickTime movies).
- Another guide from How Stuff Works.
- Probably the coolest way to get your students to explore: Atlas Gloves.
SketchUp and 3D Models
Placemarks and Overlays
As mentioned above, one of the most appealing aspects of Google Earth is the ability to import and plot information on top of the virtual globe. Placemarks and overlays are distributed as KML (Keyhole Markup Language) or KMZ (compressed KML) files, which can be opened (by selecting Open from the File menu) in Google Earth. KML/KMZ files (I'll refer to both as KML) can be opened in either version of Google Earth.
After you open a KML file, it shows up in your Google Earth browser in two ways:
- In the main window, the file shows up as placemarks (dots or icons, lines, or polygonal areas) or overlay images. Clicking on the icon of a placemark in the browser window will cause a small window to pop up. These popup windows typically show more information about the placemark (a description of a volcano, a photograph, a web link, etc.).
- In the "Places" pane (middle of the left side of the Google Earth window), you may notice the names of your placemarks or placemark collections. Clicking on the name of a placemark will zoom into that placemark in the browser window. Otherwise, the Places windowpane is similar to the Table of Contents in ESRI's ArcGIS products, or the Folders pane in Microsoft's Windows Explorer. Clicking on the triangles next to the names of placemark collections or folders will list the contents of the collection.
Some placemarks or placemark collections are dynamic, in that they contain information that changes through time. For example, the USGS has a placemark collection that shows all earthquakes that have occurred over the past 7 days. Obviously this will change as time goes by - earthquakes that occurred more than 7 days ago will be dropped from the list, and new ones will be added. The placemark collections from the USGS automatically update the list of earthquakes once you have downloaded and opened the KML file. Dynamic placemarks or collections are called network links in the Google Earth lingo.
You can make your own KML files: see below.
Google Earth Data Sources
- Google Earth Hacks
- Google Ocean
- Google Earth Community Forums - lots of links interspersed with posts
- A really neat geology/Google Earth blog, courtesy Ron Schott, Fort Hays State University, KS
- Earth Explorer and Google Sightseeing: links to various interesting locations (Earth Explorer is organized by geographical location)
Useful Google Earth Datasets
- Volcanoes! Eruptions over the past week from VolcanoWorld. Active volcanoes from the Smithsonian.
- Earthquakes! Past 7 days via the USGS (Network Link). Past 12 years from NEIC via someone in Russia. The latter may be more useful for illustrating plate tectonic boundaries. Also check out Quaternary faults and folds of the US, the 1906 San francisco Earthquake tour, and the virtual tour of the Hayward Fault: all goodies found on the USGS' 1906 centennial page.
- Marine Geoscience Data Systems demo data, including Alvin dive locations, GEBCO map overlays, MARGINS focus sites, Endeavor Ridge petrology, and a lot of other marine geology and geophysical data.
- Plates: Marine Geosciences Data Systems has one plate overlay. I put together a vector version of the University of Texas PLATES plate boundary data ( 679kB Aug24 06) (beware: some transform faults are mapped as ridges or trenches). This just in: the USGS has a better vector map of plate boundaries than I do!
- Glaciers: Antarctic and Arctic data from sites sponsored by the European Space Agency. Many of the placemarks are network links. Snow and ice data from NSIDC.
- Meteorites: A collection of about 26000 meteorite finds georeferenced by a Google Earth user named Majoska, from data provided by the Natural History Museum, London, and the Meteoritical Society. Suspected impact structures based on a list from the Impact Field Studies Group.
- Ocean Observing datasets from the southeastern US, courtesy of a variety of agencies.
- US Census data in KML format.
- GPSVisualizer can produce topo map overlays to view in Google Earth.
- Earth From Above photos by Yann-Arthus Bertrand as Google Earth overlays. Could make a good "where in the world" game.
- Water: NRCS water supply forecasts, USGS streamflow gages (here, too), and Principal groundwater aquifers of the US.
- Dinosaurs? Someone really ought to put together placemarks for all of the dinosaurs visible from the sky. There are some in London, and then there are the duo made famous by Pee-Wee Herman by the side of I-10 between LA and Palm Springs (see this article for some interesting and disconcerting recent history).... and others...
Tools for Making Placemarks and Overlays
- Arc2Earth: convert ArcGIS shapefiles to KML (requires ArcGIS). This tool costs money and is not the only ArcGIS-GE converter around (others are listed online), but it is one of the more popular.
- GPSVisualizer: a popular tool for converting GPS data to placemarks (again, not the only one).
- Panoramio: a popular way to georeference photographs (although there are others).
- EarthPlot and EarthPaint: make graphical overlays in GE. EarthPlot is useful for spatial statistics.
- Tools to create paths and graphs in Google Earth.
Examples of Good Use of Google Earth
- Google Earthing: like geocaching, but virtual. Find the locations of satellite photos.
- The USGS virtual tour of the Hayward Fault is an extremely rich information source.
- A pretty cool exercise in problem solving: when was this image made?
- I'm not an archaeologist, so I can't assess their validity, but James Jacobs, an anthropology and computer instructor at Mesa CC and Central Arizona College, has some really neat placemarks that link to extensive writeups of two sites in South America: Casma Valley ( 4kB Oct5 06) and Caral Supe ( 3kB Oct5 06), Peru.
- Two suggestions (1, 2) of how podcasting could eventually become integrated with Google Earth. I think this might do wonders for the "self-guided field trip:" a student could find a location - say of a geologic feature near his/her house - on Google Earth, downolad the coordinates into his/her GPS or GPS-enabled cell phone, and downoload a podcast tour onto his or her iPod. The student could see the actual geology for him or herself (much better than a virtual field trip) along with a "virtual" guide. I'm going to try this during the coming year....
Using Google Earth in Geoscience Education
Here are a few general suggestions for ways you might be able to incorporate Google Earth into your Earth Science classroom:
- Topographic map interpretation: using GPSVisualizer, you can create topographic map overlays, which can be viewed at different angles (and different vertical exaggerations) in Google Earth. This could supplement the plastic topo map models that many classrooms have. I sometimes show my students pictures of a location, and try to have them determine from a topographic map where the photo was taken - I can imagine doing this with GE, GPSVisualizer, and Panoramio (or a similar set of tools). If you need better terrain models than Google Earth's SRTM topography, you might check out the KML Exporter for SceneExpress, for use with LIDAR, etc.
- Measurement: Google Earth's tools could allow students to collect quantitative data by measuring elevations, distances or areas. For example, students could measure and compare the relative sizes of basaltic versus andesitic volcanoes (with caveats of course!), or could determine plate velocities from ocean island - hotspot distances (again, with some discussion of the pitfalls...).
- Decision-making: Students could use placemarks and overlays to explore the use of geographic data in decision-making (e.g. where to site a nuclear plant, a dump, or a wind farm). In this respect, Google Earth is not quite as good as a full-featured GIS, since you can't ask it, for example, "which dump sites are in a different watershed from our drinking water source?" However, for most introductory students, Google Earth's features will be sufficient to make some conclusions.
- Field trips: Although the idea of virtual field trips has been around for a while, Google Earth (and its cousin Google Maps) has the potential to greatly improve real field trips - giving students a preview of trip locations, overlaying other data on top of scenery, and (most exciting from my point of view) the ability to share field trip sites with other instructors....
- Visualizing Abstract Phenomena: Google Earth's overlays and SketchUp models should allow you to make thematic maps (in 3D!) of hard-to-grasp features such as gravity, magnetic anomalies, or EM survey data. Here's an example of an electromagnetic survey disguised as art. It's a man-made feature rather than something geological, but it illustrates the concept. I'm imagining something like gravity surveys overlain on top of this region ( 667bytes Oct5 06) in the Gulf of Mexico....
Case Studies: Using Google Earth in Geoscience Education
- An entire SERC website dedicated to teaching with Google Earth, containing many examples of activities.
- From the Cutting Edge structural geology website, Teaching Geologic Map Interpretation with Google Earth, which includes a Gallery of Google Earth Images for teaching geologic map interpretation.
- From Aida Awad, Maine East High School: Google Earth Map Analysis (Microsoft Word 44kB Aug24 06). Students compare topographic maps to images and topography from Google Earth. Contains a few questions that involve measurement (primarily of elevation).
- From Erica Cline, UW Tacoma: Federation Forest Pre-Lab (Microsoft Word 42kB Oct5 06). Introductory biology students use Google Earth to prepare for a field trip by determining whether Federation Forest (a Washington State Park) is large enough to protect habitat for a breeding pair of spotted owls.
- From Digital Geography / Juicy Geography: Montserrat simulation. Uses Google Earth and other software to make a scenario (similar to the Sleeping Mountain) come alive.
- Earthquake hazards in San Francisco planning exercise, again from Juicy Geography.
- Another good Juicy Geography idea: Diamond Trade. Investigate diamond mining and the diamond industry, both from a social and environmental point of view. I wonder if there's a way to use desire lines in this exercise.
- Teaching with GPS and Google Earth... again from Juicy Geography... you can see how much I love that site.
- More ideas (and more on the basics of GE) from Alan Rodgers.
- A collection of lessons from David at GE Lessons.
- Do you have any more ideas? Let me know!
Keyhole Markup Language (KML): Building Placemarks and Overlays by Hand
If you are intrested in creating your own placemarks but are daunted by the possibility of having to pay for GE Pro, do not fear! The free version of GE does allow you to produce placemarks and overlays (the latter is true in the Mac version; I am not sure about the Windows version). There are a number of tutorials on making placemarks (KoKae Screencasts has a good one from February 23, 2006), which can be accomplished with the click of a button in all versions of Google Earth.
Looking under the hood of placemarks and overlays is not difficult - KML files are essentially text files and can be edited in a text editor. If you want to build your own placemarks and overlays, it is useful to be able to edit the KML manually. This way you can make lines of different colors, add annotation, etc. The Google KML tutorial is here. The tutorial is written for KML version 2.0; version 2.1 is currently being beta-tested. Documentation for the two versions is here: 2.0, 2.1.
Collaborative editing (usually in the form of wikis) has become one of the buzzwords in the Web world of late. You can make collaborative placemark collections using the EditGrid online spreadsheet: here's how from Alan Glennon, UCSB. Also from Alan Glennon: collaborative placemarking by email. And another idea, this time from disaster relief collaboration Strong Angel III: collaborative placemarking by SMS (text messaging from cell phones).
Finally, if you want to make your Google Earth placemarks more widely usable, you can incorporate them into Google Maps. They can then be viewed directly in a Web browser using the Google Maps interface.